Method for the manufacture of spark plugs



YJuly 14, 1942,y G, M PAULSON 2,289,676

r H v m 2 1 original Filed Aug. 21, 1940 METHOD FOR THE MANUFACTURE 0FlSPARK PLUGS U Afl 'HEEL- 'NvENToR GE E MPAuLsoN M A'n-ToRN lmetlilower-.bod

Patevedaelyf14 ,1.942A

. April 28, 1942.

.- AOriginal"applieatioxii filed August 21, 1940,lSerial.::No."353,445`, nowPatent-No.` 2,280,972, dated .f

Divided and` this 4applicatie ...mea Janna-1941. serial 10.397.652 1- Y''z'clims. f (Cl. 29= 155.5 1)jr .This invention, 'isan improvedmethodior the manufacture of .spark-plugs and spark-plug coreassembliesf, ,The'nyention relates moreparticularl'y. though notneessarilyxclusively, to the manufacture .of :micadnsulated plugs. ...v

:Objectsare to facilitate. and simplify.mann` facture, and to insureclose tsbetween elementsofthegcoreiassembly., These-and other objectsand advantagesv of lthe* invention, and .the mannerV inv which;t l1ey-.z tre naalizedl,y will become apparentzas .the Speeiatonnrroeeda,This-application .is dlivisionef Serial. N11-'113.53.45a .le-Cl Allgutf21?. 1.94.01- `110W PatentNl-;2,280,972,`granted April-,28, 1942. Inthe-:accompanying drawing, .forming-a raft 0d .of #making .thecore/assemblati: .the .sparkplug shown in Fig. 1. Y

electrodesJ I, a n'd annpper metal body I2 which hreadsintoihe Shell.|.a-r.1.d. mr re.SS.eS @gasket I3lagainst thetopof thefshell. The lowerpart otthisupper bodycorrespondstowhat. in sparkf plugconstruction,issometimes referred to as av coupling nut. opening Ilthrough theuppermetal body I2 vtapers .toward its lower end, e..

lapplication y ENTI-OFFICE v the-upwardlyfincreasing section of thisVspindle facilitates heat conduction radiation.u

`'Iheupper end of the spindle. I5 terminates well l below vthe upper endof, the `-body I2, leaving..a shieldingbarrel.24` at the upper region ofthe spark-plug, lined bythe insulating cigarette 2 I.to'receivean'insulatedconductor.,

lThe methodby-whichthe core assembly is put 'together during manufactureis partly illustrated mightgmake agood lit Withthelower end of the lInthe`method of this invention the small amount i siyely smaller towardits.` lower end..`

,A downwardly tapering spindl I6 lower. end.` Thishead is large enoughto form an annular shoulder I9. on the spindle.. An in-y sf COIIStilinE-a. center electrode, welded to its sulatingsleeye or cigarette', 2 I .ofmica insulation, r

tightly wrapped, is directly,interposed'betweenthe tapered .surfacesgoffthe spindle I6" .and fthe' opening I 4.. "Ihissleeye or cigaretteextends from body of the plug;` l

fAn additionalbody of insulation, preferably consisting of a stack' ofvmicaA washers 22, isV held under compression between the shoulder`l9and the shoulder .I9ftojthe top of `the part I2 "of the" y arecessed`face 'at tthe bottomof the body part I2, and closely surrounds thelower'fportion-of the mica cigarette 12|... The spindle I6 preferablyconsists of a tube I'i of steelxaor other suitable metal, which tapersVboth outside andminside, .and ataperedinsert 23 by Fig.` 2.- Thecoreassembly may be said to include the'rnetal bodyllpart I2, thespindleI6, lor itsry element I1,- :the spindle head` I8, and the. in-

An important feature 'offthe method is .that e the insulation 2l, 22 isassociated 'with the spindle, orthe spindleelement I1 before the head`I8 is welded `tothe spindle, ,and is in place when 3 the weldingoperation is performed. This makes unnecessaryal subsequent Amachiningoperation to remove external flash-or extruded, metal, at the junctionbetween the spindle and the spindle head.'A In former practice, spindleIheads were weldedto spindles beforethe insulation `was applied, anditwas necessary to machine away the -ash in order that, thereafter, theinsulation spindle and theshoulder of the spindle head.-

of flash that is `formedtends to ll any' air space that there may be at,this region, andto that extent is beneficial. Y Y f.

"The methodofassembling Vand securing the core elementswill now be moreAparticularly den,

scribed, ibu`t it will be understood that. details may be..varied,= Thestackof washers 2.2l is placed in a clamping nutv 40. whicndoes not formpart .0f the .Spark-.

plug.- Thisnut and'thevybodyfelement I2 are I then screwed together, the nut.V .engaging the threads which-.later connect the body I2 with thelowerl body or. shell Il).` The stack of. washers is held, in position,Vand is tightly compressed endwise of the- -stack between a shoulder inthey clampingnutand the recessed'end face of the of copper or.. othermaterialy'of relativelyV high heat conductivity. Such inserts aid inconducting heat away from the center electrode I8, and

body I2. The bore of thestackof washers isl taper reamed so that itwilltthe tapered cigarette..`

yThe cigarette-"2| ,is tightly wrapped about a mandrel v having the same-taper as theA spindle I6.` This mandrelwith the cigarette on it is in-`serted into the 4tapered opening of the body I2 and the tapered bore ofthe stack of Washers. The mandrel is lthen removed. leaving the ciga-`rette in place. At a suitable time the ends of the cigarette aretrimmed.

Nowthe hollow spindle element I'I is insert-A ed into the cigarette. Theparts are thenas shown in Fig. 2. This assembly is placed'on an electricresistance welding machine by slipping the spindle element I1 over atapered electrode 42 of` the welding machine. The spindle head I8 isheld by a chuck 43, which is the second electrode of the welding.machine. Oneor both of the electrodes of the welding machine move towardand from the other in a manner well understood in the art, and theopening in the end of the clamping nut 40 serves as a guide. foraccurately positioning the head I8' withl respect to the hollow spindleas the two are brought together for welding.

The spindle head is pressed forcibly against CIK the end of the hollowspindle and the current is turned on. The heat and pressure causevmeta-l to flow forming a certain amount of` external flash which isaccommodated by the mica in sulation andhelps to close any air space.However, the arnount ofash is relatively small, andl not sufiicient toinjure' the insulation, since the stack of washers 22` acts as a stopfor the .head I8 in the welding operation and limits the amount of metalthat is extruded. The pressure on the spindle head in the weldingoperation places some additionalcompression on the stack of washers,though this need not be the case. In any event the stack isnowclampedlbetween the head I8 and the body I2.

They assembly is then removed from the-.elec-v trode 42, andi the nut 40is removed from the body I2.. The stack of washers is then preferablymachined tothe externa-l taper shown'iin Fig. l. The insert 23` isdriven into the hollow spindle element I1.

When the body I2'is` screwed into the shell IIlthe construction ofthespark-plug properis complete.

In former practice it was customary to wrap -a mica cigarette about'. a`cylindrical spindle before the cigarette was wrapped. In that operation'it was not' easy to'get. a, good t between the lower end of4 the.ycigarette and thev shoulderofy the head. With the* method which has beendescribed in this specication the cigarette need not be woundwith,itsend against av shoulder. In the welding operation the shoulder of thehead is broughtI tight against the lower end of the cigarette as well asagainst the lower endof the stack of mica washers.

Because of the tapered construction the mica cigarette can be moretightly wrapped than the customary; cylindrical cigarette, also atighter t can be obtained between the cigarette andthe bore of thestaclrof washers. Inthe core-assembly the cigarette is held tightlybetween the tapered spindle andthe tapered opening in the body I2. It istightagainst the washersA and tight against the spindle head.

The body of insulation 221is preferably composed of' a stack of micawashers, as herein described. However, the invention, in a broaderaspect, is not necessarily limited to this type of insulation, sinceinsulation of other material or construction could b e substituted.

Terms ofV orientation, such as upper and lower, refer to the position ofthe spark-plug shown in the drawing, not vto the position which it mayoccupy in use. The lower end of the spark-plug is the inward end inrelation to the engine cylinder, and the upper end is the outward end.

I claim:

1. In the manufacture of a spark-plug, the

method which comprises associating a spindle, an insulating sleeve aboutsaid spindle, a sparkplug body around the upper portion of the sleeve,and a body of insulation around thelower portion of the sleeve andpressed up against the spark-plug body, and with the parts lin suchassembled relation welding a head to the lower end of the spindle inposition to keep the body of insulation on the insulating sleeve andagainst the spark-plug body.

2. In the manufacture of a spark-plug, the method which comprisesassociating a spindle, a mica cigaretteA about said spindle, and a stackof mica washers about the lower part of said cigarette, pressing a headagainst the lower end of the spindle, cigarettev and stack with thecigarette and` stack in place on the spindle, and with the head in suchposition weldingv the head to the lower end of the, spindle.

3'.l In the manufacture of a spark-plug, the method which comprisesassociating a spindle, a mica cigarette about said spindle, and a stackof mica washers about the lower part of the cigarette, holding the stackof washers under compression andwith the stack so held, pressing a headagainstthe lower end of the spindle and welding the head to the lowerend of the spindle in positionto keep the stack inv-place and undercompression..

4. In the manufacture of aspark-plug, the method which comprisesproviding a downwardly tapered spindle and a metal body'having adownwardly tapered opening, windinga tapered mica cigarette, providinglabody of insulation having a downwardly taperedbore, associating theforegoing elements with said eigarette'directly between saidtapered'spindle andthe taperedsurface of the opening in said metal body,and said body of insulation'about the lower part of said cigarette, andthereafter holdingt the parts assembled by welding a head'` to the.lower end of said spindle withv saidl body of insulation clamped`between said head andthe lower metal body.

5. In the manufacture'of a spark-plug', the method whichv comprisesproviding a downwardly tapered spindle and a metal body having adownwardly tapered opening, Winding a tapered mica cigarette, providinga stack of` mica washers having adownwardly tapered. bore, associatingthe foregoing elements with said cigarette directly between said taperedspindle and the tapered surface of the opening in said metal body, andsaid stack of washers about the lower part of said cigarette, and`thereafter welding, a head to the lower end" of said spindle, the headybeing brought' tight against the lower ends of said cigarette and saidstack` of washers to hold said stack of washers between said head. andthe lower portion of said metal. body and' maintain all of the parts inassembled. relation.

6. In the manufacture of a spark-plug, the method which comprisesproviding a downwardly tapered spindle and a metal body having adownwardly tapered opening, clamping, a stack of mica washers againstthe lower portion of said metal body, taper reaming` the bore ofy saidstack of washers, wrapping a mica cigarette on a tapered mandrel,inserting said cigarette into the tapered opening of said metal body andthe tapered bore of said stack of washers, inserting said spindle intosaid cigarette, and thereafter welding a head to the lower end` of saidspindle.

7. In the manufacture of a spark-plug, the

portion of said method which comprisesassembling a stack of insulatingWashers,`giving said stack a tapered bore, forming a tapered insulatingcigarette on a tapered mandrel, inserting `said cigarette into thetapered bore of a metal body, inserting a tapered spindle member intosaid cigarette, compressing the stack of washers on the taperedcigarette, and while holding said stack of washers compressed welding ahead to the lower end of said spindle member in close contact with theend of said cigarette and in position to keep the stack of washerspressed together after the force compressing the stack of Washers isremoved.

t GEORGE M. PAULSON.

